Tbical manupactubina cobpobation



G. E. JANSSON OIL FILLED INSULATING BU`SHING Jan. 1`, 1929.

Filed Dec. l, 1926 Patented-lan. lll', ,1929;

eUs'rAv'lN. JANssoN, or woILLAs'roN, miAssAcnUsE'rrs,

l ASSIGNOR TO CONDIT ELEC- TRICAL MANUFACTURING CORPORATION, or sown nos'roN, MAssAcHUsarrs, A

QORAPOBATION F MASSACHUSETTS.

.OIL-FILLE INSULATlING RUSHING.

' Axipnomon ma December 1, isae. 'semi No. 152,030. I,

This invention relates to insulating bush` ings for the protection of, high tension leads of metal enclosed electrical apparatus and particularly to insulators of this type which are adapted to be filled with an insulating fluid or compound, such as oil.

Porcelain 1s generally used for the outer' tubular casing of the bushing which forms a container for the insulating fluid within, and due to the great length of bushing required in high tension apparatus these tubes are necessarily made up of several sections sev cured together in a suitable manner to provide a long, fluid-tight insulating tube. Cement is employed to provide the mechanical bond between the several sections of the tube but, due toJi'ts porous structure, cement can ble in practice or for other reasons have beenobjectionable. I

It is an object of this invention to provide a high tension Amulti-part insulatin bushing with means by which fluid-tight joints are provided between the parts in an inexpensive and effective manner.

A still further object is generally'to improve the construction and performance of oil filled insulating bushings.

Fig. 1 is an elevation partly in section of an insulator embodying the invention. Fig. 2 is an enlarged sectional detail of the insulator of Fig. 1 in the vicinity of the supporting fiange, showing the fluid tight joint between the two insulating sections.

' Fig. 3 is'a section of an insulator similar to Fig. 1 showing a modied form of oil seal.

As here shown, the insulating bushing embodying the invention comprises the upper insulatlng section 10 provided with the usual capes or petticoats 12, the lower insulating I section 14 provided with external corrugations 16 at the lower end thereof, and the intermediate metal attaching collar, or sleeve 18, which surrounds the proximate ends of said sections 10and 14. The'upper insulatin section comprises eentially a porcelain tu e preferably -havingstraight side walls and being open at the top and bottom. The

lower lnsulating section `com rises a porcelain tube open at the top an tapered at its lower end `to provide a restricted passage at the bottom.

The insulator is provided at the top with an oil reservoir consisting of a metalcylinder 2O which is secured in fluid tight relation to the open top of the upper insulating section 10. The oil reservoir is provided with a cap 24 which is screw-threaded to the upper end of said cylinder 2O and forms a cover for the reservoir. A glass cylinder 26 is disposed within said cylinder 20 and the oil level in the insulator andin the glass cylinder 20 is visible through suitable apertures 28 of. the metal cylinder 20. Said reservoir cover 24 is provided with an upstanding projection 29 having an axial passage therein through which a conducting stud 32 is adapted to pass freely. Said opening is protected against entrance of water by a cover .34 which is screw-threaded on said conductor and which has a depending apron 36 surrounding the projection 29.

The restricted passage at the lower end of the insulating section 14 is provided with an axial bushin 38 secured therein by means of cement 40. gaid conducting stud 32 is adapted to be screw-threaded through and extend beyond said bushing and a lock nut 41 is screwed onto Ithe lower extended end thereof to prevent rotation of the stud in the bushing.

An oil tight seal is provided at the lower end I 42` disposed beofthe insulator by a packing insulating sectween the lower end of sai tion 14 and the nut41. i

The metal collar 18 is `adapted to provide a mechanical connection between the upper and lower insulatin sections and also to provide a support for t e insulator and said colylar is provided with an integral outstanding flange 44 by which the bushing is adapted to be secured to the casing 46 of an electrical apparatus. Said collar is adapted to be somewhat larger in diameter than the two insulating sections to provide an annular space. therebetween tol receive a body of cement 47 bymeans of which said upper and lower insulating sections are rigidl and permanently fixed ywithin said col ar 18. Annular grooves 48 are formed on the inner surfaces of said collar into which the cement may enter, and these surfaces of the insulating sec tions which are surrounded by said collar may be roughened, thus enhancing the strength of the mechanical bond between the metal collar and the insulating sections. The lcemented joint between the insulating sections 10 and 1 4 provides a permanent, unitary structure for the enclosing casing of the bushing which is adapted to remain intact when once assembled.

There is no necessity for subsequently breaking the joint between 'the sections since the open top construction permits the removal and assembly of the inner` parts of the bushin through the top as set forth in my co-pen ing application Serial No. 110,126, filed May 1-9, 1926.

As previously stated, cement where used between sections of oil iilled bushings cannot always be relied upon to maintain an effective oil tight seal thereat because of its inherent porous structure. Consequently it is necessary to provide additional fluid sealing means wherever the oil has access to the cement.

In accordance with m invention an external coating of elastic, fluid-impervious material is provided at the top and bottom of the metal collar 18 as shown in Figs. 1 and 2. 'Previous to applying this coating, the porcelain surfaces to be covered preferably are somewhat roughened as by grinding, and annular' grooves 52 are ground or otherwise formed 1n the outer surface of the insulating sections 10 and 14 just beyond the level of the body of cement 47 to avoid a sharp angle in the coating at the junction of the cement and the insulating section, and also to provide a more secure bond between the coating and the porcelain. y

The inner surfaceof said metal collar 18 may be provided with annular serrations 53,

-see Fig. 3, in the vicinity of the elastic coating if desired to increase the surface of adhesion and Iprevent any tendency of the coating to pul away from the metal surfaces upon expansion and contraction thereof.

Said Huid-impervious coating may com- .prise any tough, elastic inorganic substance such as a metal. In the embodiment of the invention herein shown, I have chosen to employla metallic substance to provide the Huid sealing coating.

The metal for the coating material is ap-V plied -by the hot metal spray process, by which the metal is deposited in a very thin continuous iilm of finely divided molten particles, which particles are forcibly thrown onto the surface and into the pores of the surface upon which it is directed, thereby forming a strong mechanical bond with the surface and the film, which, while prefer.

ably thin, is very strong and tenacious. The metal can be applied continuously until the required thickness of iilm has been deposited, the amount of metal which it is desirable to operating conditions to whichjthe insulatoris to be'subjec'ted; and the particular metal or alloy of metals employed will be governed among other things, by the considerations'o expansion and contraction of the'associated parts of the insulator.

The metal Coating or sheet is characterized by being fluid-impervious so that oil which may seep into the cement bycapillary action is prevented from escaping from the outer surface thereof. The coating is closely adherent to all the surfaces and enters the ores and irregularities of the surfaces whereiby it is, in eiect, bonded thereto. The coating is iiexible to permit a small amount of relative movement between the surfaces to which it is adherent without rupture and is ductile so that it can stretch the small amount neces-v sary to prevent rupture.

The metal coating 54 at-the top of said collar 18 extends from the collar 18 to a point beneath the lower cape of the insulating section 10, and the lower metal coating 56 is extended to a point below the level of the oil in the casing 46 of the electrical apparatus. A single turn of wire 58 of substantial diameter to which the metal coating will adhere is disposed about the lower insulating section14 at this point to provide a suitable termination of the metal ground shield thus formed and also more evenly to distribute the electrical stresses 'at the end of said ground shield.

Fig. 3 is a modiiieel form of the oil seal shown in Figs. 1 and 2 in which a soft protective packlng or compound 60 is placed around the metal seal after which a second metal coating 62 is built up between the colh lar 18 and the first 'metal coatings 54 and'56. In this way an elastic and yielding film of metal is provided to supplement the outer metallic seal in case it should be by any chance broken by unduly rough treatment in transportation, or otherwise.

In disclosing the invention, I have shown lthe metal seal applied-at the ends of the collar 18 which inthe particular insulator shown is the most feasible construction since the seal is made after the assembly of the insulator and l-is accessible for inspection or repair. However, it is possible, and in some constructions practicable, to apply the metal coating directly tothe juxtaposed ends of the insulating sections and to the exterior of the bushing Ain the immediate vicinity of the joint previous to cementing the supporting collar 18 1n place. Various other modiiications in the manner of applying the metal seal may be employed without departing from the scope of the present invention.

I claim:

1. An oil-iilled insulating bushing including two adjacent sections, a fluid permeable -body interposed between said vsect-ions having its inner surface in contact with the oil within the bushing, and an elastic, fluid-impermeable metal coating covering the outer surface of said body.

Q. An oil-filled insulating bushing having an insulating shell, an attaching sleeve surrounding the shell, a body of cement disposed between saidfsleeve and said shell and exposed at its inner surface to the oil in the bushing, and means providing a duid-tight seal for the outer exposed surface of said cement body, said means comprising a coating of fluid-impervious metal adherent to the cement and also to the adjacent surfaces of said shell and said sleeve.

3. .An oil-filled insulating bushing having an insulating shell, an attaching sleeve surrounding the shell,y a body of cement disposed between said sleeve and said shell and exposed at its inner surface to the oil in the bushing, and means providing a Huid-tight seal for the outer exposed surfaces of said cement body, said means comprising a thin Huid-tight metal sheet closely conformed to the surfaces of the sleeve, cement bod)v and shell and strongly adherent to said surfaces.

4. An oil-filled insulating bushing having an insulating shell, an attaching sleeve surrounding the shell, a body of cement disposed between said sleeve and said shell and exposed at its inner surface to the oil in the bushing, and means providing a fluidiight seal for the outer exposed surface of said freinent body, said means comprising a thin fluid-tight metal sheet closely conformed to the surfaces of the sleeve` cement body and shell and strongly adherent to said surfaces, said sheet being .characterized by being flexible and-ductile;

5. Anoil-filled insulating bushing including a pair of spaced members having an interposed-body of cement connecting them, whichbody is exposed at its inner exposed surface to the oil in the bushing, and means to seal the outer exposed surface of the cement body against escape of oil therefrom comprising a thin and flexible oil-tight metal coating coveringr the outer end of the cement body. and the adjacent surfaces of said spaced members and .strongly adherent therewith.

6. An oil-filled insulating bushing having two axially aligned insulating members, a collar disposed around the proximate ends of said members and spaced therefrom. a body of cement contained in the space between said collar and said members to bind said collar tight and strong mechanical bond therewith.

8. An insulating bushing having an insuA lating oil-containing shell. a metal follar surrounding said shell intermediaul its ends. a body of cement located between said collar and shell and exposed to the oil in the `shell. a metal ring surrounding said shell below said collar, 4and a metal coating connected intimately with said collar and shell and with said ring and overlying and forming an impervious vfluid seal for said-cement bushing between said collar and shell.

In testimony whereof, I have name to this specification.

GUSTAV E. JANSSON.

signed my 

